1. Field of the Invention
This invention relates to the treatment and neutralization of corrosive compounds and acid buildup in the flue gas and flue gas condensate of coke-fired industrial heating devices during shutdown, and more particularly, in the flue gas ductwork, piping, and downstream heat exchangers of a coke-fired foundry cupola of the type used in making pig iron or ductile iron from scrap iron.
2. Description of Related Art
Coke is used as the primary heating source for the melting of scrap iron in a foundry cupola. Because of the sulfur content in coke, sulfurous compounds are formed during combustion and exit the cupola in the flue gas. Water vapor created as a byproduct of combustion is also present. As long as the flue gas temperature stays above the dew point of water, the water will not react with sulfur dust entrained in the flue gas. However, many such cupolas are not run continuously, and during the shutdown phase of cupola operation, after the blast air is removed from the tuyeres, a fine water mist is sprayed into the flue gas stream to provide additional cooling. When the flue gas falls below 300° F., all wind to the unit is stopped. At that time, the cap to the combustion chamber is opened to the atmosphere. This action is done to prevent carbon monoxide and other objectionable fumes from building up in the plant. As the heat and fumes escape to the atmosphere, a venturi effect causes the air stream downstream of the combustion chamber to reverse. Air starts to flow in the opposite direction as opposed to the normal operational air flow. Moisture-laden atmospheric air is drawn into the system from the bag house. As the flue gas duct work cools, the dew point is reached. The resultant condensate combines with the entrained sulfurous compounds to produce sulfuric acid, which is highly corrosive to ductwork, piping and downstream heat exchange equipment. The associated repair and replacement costs for corroded downstream equipment have made it highly desirable to reduce such corrosion.
The use of morpholine or morpholine derivatives, sometimes in combination with amine alcohols, in steam lines and, more generally, as an acid neutralizer and or pH buffer in other applications including, for example, pipelines and processing equipment for petroleum fluids, is known. Prior patents and some published pending patent applications disclosing the use of such compounds, often in combination with other compositional components, are disclosed below: U.S. Pat. Nos. 7,216,710; 6,986,358; 6,861,032; 5,916,483; 5,411,670; 5,366,643; 4,719,036; 4,120,654; 4,026,946; and 2,745,809. United States Publication Nos. 20070001150; 20050263739; 20050250666;and 20030199397. Some of the references disclose compositions useful as corrosion inhibitors that contain various amines and also contain quaternary ammonium chloride, often in combination with other compounds.